The present invention relates to a camera equipped with an automatic focusing device, and more particularly to an automatic focussing camera of the type having a taking lens system which can be changed suitably for wide-angle photography, telephotography or macro photgraphy by changing the focal length thereof.
Numerous compact cameras having lens shutters are already known. Some such compact cameras are provided with taking lenses of the type in which the focal length can be changed between a relatively short focal length of about 35 mm suitable for wide-angle photography and a relatively long focal length of about 70 mm suitable for telephotography. For changing the foacl length of the taking lens system in such a camera, an extra lens is provided which is displaced from the optical path of the taking lens when the taking lens system is changed to short focal length and, on the other hand, is moved into the optical path simultaneously with the movement of the main focusing lens of the taking lens when changing to long focal length. In many cases, the camera with a taking lens changeable between two different focal lengths is adapted to adjust the focus of the taking lens with the aid of a photoelectric automatic focusing system.
A recent tendency in such cameras is to provide a macro-photographic feature that enables taking close-up photographs of a subject, for example at a distance between about 1 and 100 cm. For this macro photography, it is necessary to extend the focusing range in which the taking lens can be correctly focused on a subject which is quite close to the camera. One problem associated with such a camera having a macro-photographic capability is the bulky and complicated automatic focusing mechanism which is required by the fact that the automatic focusing mechanism must cover a wider range of focusing distance. For covering the widened range of focusing distance, the photoelectric automatic focusing system has to have light projecting and light receiving means which are complicated in construction and large in size. Although it may be permissible to provide an extra automatic focusing system, it is not advantageous from a standpoint of cost and saving space in the camera.
Usually an automatic focusing system is adapted to adjust the taking lens system to a predetermined number of focusing distances between the closest distance and an infinite distance. Therefore, the focusing distances to which the focus of the taking lens is adjusted are set relatively roughly. If a close subject distance range, in which taking lens systems have generally had a relatively shallow depth of field, is provided with a relatively large number of distance settings, the number of distance settings will be correspondingly smaller in the normal or standard subject distance range in which photographs are usually taken most frequently. In addition, the taking lens has to have a large sliding distance in order to cover the whole subject distance range between the closest and infinite subject distances, and this increases the time required for the focus adjusting operation of the taking lens.